diff options
Diffstat (limited to 'mm/oom_kill.c')
| -rw-r--r-- | mm/oom_kill.c | 1156 |
1 files changed, 1156 insertions, 0 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c new file mode 100644 index 000000000..3f5a60a5a --- /dev/null +++ b/mm/oom_kill.c @@ -0,0 +1,1156 @@ +/* + * linux/mm/oom_kill.c + * + * Copyright (C) 1998,2000 Rik van Riel + * Thanks go out to Claus Fischer for some serious inspiration and + * for goading me into coding this file... + * Copyright (C) 2010 Google, Inc. + * Rewritten by David Rientjes + * + * The routines in this file are used to kill a process when + * we're seriously out of memory. This gets called from __alloc_pages() + * in mm/page_alloc.c when we really run out of memory. + * + * Since we won't call these routines often (on a well-configured + * machine) this file will double as a 'coding guide' and a signpost + * for newbie kernel hackers. It features several pointers to major + * kernel subsystems and hints as to where to find out what things do. + */ + +#include <linux/oom.h> +#include <linux/mm.h> +#include <linux/err.h> +#include <linux/gfp.h> +#include <linux/sched.h> +#include <linux/sched/mm.h> +#include <linux/sched/coredump.h> +#include <linux/sched/task.h> +#include <linux/swap.h> +#include <linux/timex.h> +#include <linux/jiffies.h> +#include <linux/cpuset.h> +#include <linux/export.h> +#include <linux/notifier.h> +#include <linux/memcontrol.h> +#include <linux/mempolicy.h> +#include <linux/security.h> +#include <linux/ptrace.h> +#include <linux/freezer.h> +#include <linux/ftrace.h> +#include <linux/ratelimit.h> +#include <linux/kthread.h> +#include <linux/init.h> +#include <linux/mmu_notifier.h> + +#include <asm/tlb.h> +#include "internal.h" +#include "slab.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/oom.h> + +int sysctl_panic_on_oom; +int sysctl_oom_kill_allocating_task; +int sysctl_oom_dump_tasks = 1; + +/* + * Serializes oom killer invocations (out_of_memory()) from all contexts to + * prevent from over eager oom killing (e.g. when the oom killer is invoked + * from different domains). + * + * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled + * and mark_oom_victim + */ +DEFINE_MUTEX(oom_lock); +/* Serializes oom_score_adj and oom_score_adj_min updates */ +DEFINE_MUTEX(oom_adj_mutex); + +#ifdef CONFIG_NUMA +/** + * has_intersects_mems_allowed() - check task eligiblity for kill + * @start: task struct of which task to consider + * @mask: nodemask passed to page allocator for mempolicy ooms + * + * Task eligibility is determined by whether or not a candidate task, @tsk, + * shares the same mempolicy nodes as current if it is bound by such a policy + * and whether or not it has the same set of allowed cpuset nodes. + */ +static bool has_intersects_mems_allowed(struct task_struct *start, + const nodemask_t *mask) +{ + struct task_struct *tsk; + bool ret = false; + + rcu_read_lock(); + for_each_thread(start, tsk) { + if (mask) { + /* + * If this is a mempolicy constrained oom, tsk's + * cpuset is irrelevant. Only return true if its + * mempolicy intersects current, otherwise it may be + * needlessly killed. + */ + ret = mempolicy_nodemask_intersects(tsk, mask); + } else { + /* + * This is not a mempolicy constrained oom, so only + * check the mems of tsk's cpuset. + */ + ret = cpuset_mems_allowed_intersects(current, tsk); + } + if (ret) + break; + } + rcu_read_unlock(); + + return ret; +} +#else +static bool has_intersects_mems_allowed(struct task_struct *tsk, + const nodemask_t *mask) +{ + return true; +} +#endif /* CONFIG_NUMA */ + +/* + * The process p may have detached its own ->mm while exiting or through + * use_mm(), but one or more of its subthreads may still have a valid + * pointer. Return p, or any of its subthreads with a valid ->mm, with + * task_lock() held. + */ +struct task_struct *find_lock_task_mm(struct task_struct *p) +{ + struct task_struct *t; + + rcu_read_lock(); + + for_each_thread(p, t) { + task_lock(t); + if (likely(t->mm)) + goto found; + task_unlock(t); + } + t = NULL; +found: + rcu_read_unlock(); + + return t; +} + +/* + * order == -1 means the oom kill is required by sysrq, otherwise only + * for display purposes. + */ +static inline bool is_sysrq_oom(struct oom_control *oc) +{ + return oc->order == -1; +} + +static inline bool is_memcg_oom(struct oom_control *oc) +{ + return oc->memcg != NULL; +} + +/* return true if the task is not adequate as candidate victim task. */ +static bool oom_unkillable_task(struct task_struct *p, + struct mem_cgroup *memcg, const nodemask_t *nodemask) +{ + if (is_global_init(p)) + return true; + if (p->flags & PF_KTHREAD) + return true; + + /* When mem_cgroup_out_of_memory() and p is not member of the group */ + if (memcg && !task_in_mem_cgroup(p, memcg)) + return true; + + /* p may not have freeable memory in nodemask */ + if (!has_intersects_mems_allowed(p, nodemask)) + return true; + + return false; +} + +/* + * Print out unreclaimble slabs info when unreclaimable slabs amount is greater + * than all user memory (LRU pages) + */ +static bool is_dump_unreclaim_slabs(void) +{ + unsigned long nr_lru; + + nr_lru = global_node_page_state(NR_ACTIVE_ANON) + + global_node_page_state(NR_INACTIVE_ANON) + + global_node_page_state(NR_ACTIVE_FILE) + + global_node_page_state(NR_INACTIVE_FILE) + + global_node_page_state(NR_ISOLATED_ANON) + + global_node_page_state(NR_ISOLATED_FILE) + + global_node_page_state(NR_UNEVICTABLE); + + return (global_node_page_state(NR_SLAB_UNRECLAIMABLE) > nr_lru); +} + +/** + * oom_badness - heuristic function to determine which candidate task to kill + * @p: task struct of which task we should calculate + * @totalpages: total present RAM allowed for page allocation + * @memcg: task's memory controller, if constrained + * @nodemask: nodemask passed to page allocator for mempolicy ooms + * + * The heuristic for determining which task to kill is made to be as simple and + * predictable as possible. The goal is to return the highest value for the + * task consuming the most memory to avoid subsequent oom failures. + */ +unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, + const nodemask_t *nodemask, unsigned long totalpages) +{ + long points; + long adj; + + if (oom_unkillable_task(p, memcg, nodemask)) + return 0; + + p = find_lock_task_mm(p); + if (!p) + return 0; + + /* + * Do not even consider tasks which are explicitly marked oom + * unkillable or have been already oom reaped or the are in + * the middle of vfork + */ + adj = (long)p->signal->oom_score_adj; + if (adj == OOM_SCORE_ADJ_MIN || + test_bit(MMF_OOM_SKIP, &p->mm->flags) || + in_vfork(p)) { + task_unlock(p); + return 0; + } + + /* + * The baseline for the badness score is the proportion of RAM that each + * task's rss, pagetable and swap space use. + */ + points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + + mm_pgtables_bytes(p->mm) / PAGE_SIZE; + task_unlock(p); + + /* Normalize to oom_score_adj units */ + adj *= totalpages / 1000; + points += adj; + + /* + * Never return 0 for an eligible task regardless of the root bonus and + * oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here). + */ + return points > 0 ? points : 1; +} + +enum oom_constraint { + CONSTRAINT_NONE, + CONSTRAINT_CPUSET, + CONSTRAINT_MEMORY_POLICY, + CONSTRAINT_MEMCG, +}; + +/* + * Determine the type of allocation constraint. + */ +static enum oom_constraint constrained_alloc(struct oom_control *oc) +{ + struct zone *zone; + struct zoneref *z; + enum zone_type high_zoneidx = gfp_zone(oc->gfp_mask); + bool cpuset_limited = false; + int nid; + + if (is_memcg_oom(oc)) { + oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1; + return CONSTRAINT_MEMCG; + } + + /* Default to all available memory */ + oc->totalpages = totalram_pages + total_swap_pages; + + if (!IS_ENABLED(CONFIG_NUMA)) + return CONSTRAINT_NONE; + + if (!oc->zonelist) + return CONSTRAINT_NONE; + /* + * Reach here only when __GFP_NOFAIL is used. So, we should avoid + * to kill current.We have to random task kill in this case. + * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. + */ + if (oc->gfp_mask & __GFP_THISNODE) + return CONSTRAINT_NONE; + + /* + * This is not a __GFP_THISNODE allocation, so a truncated nodemask in + * the page allocator means a mempolicy is in effect. Cpuset policy + * is enforced in get_page_from_freelist(). + */ + if (oc->nodemask && + !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) { + oc->totalpages = total_swap_pages; + for_each_node_mask(nid, *oc->nodemask) + oc->totalpages += node_spanned_pages(nid); + return CONSTRAINT_MEMORY_POLICY; + } + + /* Check this allocation failure is caused by cpuset's wall function */ + for_each_zone_zonelist_nodemask(zone, z, oc->zonelist, + high_zoneidx, oc->nodemask) + if (!cpuset_zone_allowed(zone, oc->gfp_mask)) + cpuset_limited = true; + + if (cpuset_limited) { + oc->totalpages = total_swap_pages; + for_each_node_mask(nid, cpuset_current_mems_allowed) + oc->totalpages += node_spanned_pages(nid); + return CONSTRAINT_CPUSET; + } + return CONSTRAINT_NONE; +} + +static int oom_evaluate_task(struct task_struct *task, void *arg) +{ + struct oom_control *oc = arg; + unsigned long points; + + if (oom_unkillable_task(task, NULL, oc->nodemask)) + goto next; + + /* + * This task already has access to memory reserves and is being killed. + * Don't allow any other task to have access to the reserves unless + * the task has MMF_OOM_SKIP because chances that it would release + * any memory is quite low. + */ + if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) { + if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags)) + goto next; + goto abort; + } + + /* + * If task is allocating a lot of memory and has been marked to be + * killed first if it triggers an oom, then select it. + */ + if (oom_task_origin(task)) { + points = ULONG_MAX; + goto select; + } + + points = oom_badness(task, NULL, oc->nodemask, oc->totalpages); + if (!points || points < oc->chosen_points) + goto next; + + /* Prefer thread group leaders for display purposes */ + if (points == oc->chosen_points && thread_group_leader(oc->chosen)) + goto next; +select: + if (oc->chosen) + put_task_struct(oc->chosen); + get_task_struct(task); + oc->chosen = task; + oc->chosen_points = points; +next: + return 0; +abort: + if (oc->chosen) + put_task_struct(oc->chosen); + oc->chosen = (void *)-1UL; + return 1; +} + +/* + * Simple selection loop. We choose the process with the highest number of + * 'points'. In case scan was aborted, oc->chosen is set to -1. + */ +static void select_bad_process(struct oom_control *oc) +{ + if (is_memcg_oom(oc)) + mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc); + else { + struct task_struct *p; + + rcu_read_lock(); + for_each_process(p) + if (oom_evaluate_task(p, oc)) + break; + rcu_read_unlock(); + } + + oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages; +} + +/** + * dump_tasks - dump current memory state of all system tasks + * @memcg: current's memory controller, if constrained + * @nodemask: nodemask passed to page allocator for mempolicy ooms + * + * Dumps the current memory state of all eligible tasks. Tasks not in the same + * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes + * are not shown. + * State information includes task's pid, uid, tgid, vm size, rss, + * pgtables_bytes, swapents, oom_score_adj value, and name. + */ +static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask) +{ + struct task_struct *p; + struct task_struct *task; + + pr_info("Tasks state (memory values in pages):\n"); + pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n"); + rcu_read_lock(); + for_each_process(p) { + if (oom_unkillable_task(p, memcg, nodemask)) + continue; + + task = find_lock_task_mm(p); + if (!task) { + /* + * This is a kthread or all of p's threads have already + * detached their mm's. There's no need to report + * them; they can't be oom killed anyway. + */ + continue; + } + + pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", + task->pid, from_kuid(&init_user_ns, task_uid(task)), + task->tgid, task->mm->total_vm, get_mm_rss(task->mm), + mm_pgtables_bytes(task->mm), + get_mm_counter(task->mm, MM_SWAPENTS), + task->signal->oom_score_adj, task->comm); + task_unlock(task); + } + rcu_read_unlock(); +} + +static void dump_header(struct oom_control *oc, struct task_struct *p) +{ + pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n", + current->comm, oc->gfp_mask, &oc->gfp_mask, + nodemask_pr_args(oc->nodemask), oc->order, + current->signal->oom_score_adj); + if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order) + pr_warn("COMPACTION is disabled!!!\n"); + + cpuset_print_current_mems_allowed(); + dump_stack(); + if (is_memcg_oom(oc)) + mem_cgroup_print_oom_info(oc->memcg, p); + else { + show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask); + if (is_dump_unreclaim_slabs()) + dump_unreclaimable_slab(); + } + if (sysctl_oom_dump_tasks) + dump_tasks(oc->memcg, oc->nodemask); +} + +/* + * Number of OOM victims in flight + */ +static atomic_t oom_victims = ATOMIC_INIT(0); +static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait); + +static bool oom_killer_disabled __read_mostly; + +#define K(x) ((x) << (PAGE_SHIFT-10)) + +/* + * task->mm can be NULL if the task is the exited group leader. So to + * determine whether the task is using a particular mm, we examine all the + * task's threads: if one of those is using this mm then this task was also + * using it. + */ +bool process_shares_mm(struct task_struct *p, struct mm_struct *mm) +{ + struct task_struct *t; + + for_each_thread(p, t) { + struct mm_struct *t_mm = READ_ONCE(t->mm); + if (t_mm) + return t_mm == mm; + } + return false; +} + +#ifdef CONFIG_MMU +/* + * OOM Reaper kernel thread which tries to reap the memory used by the OOM + * victim (if that is possible) to help the OOM killer to move on. + */ +static struct task_struct *oom_reaper_th; +static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); +static struct task_struct *oom_reaper_list; +static DEFINE_SPINLOCK(oom_reaper_lock); + +bool __oom_reap_task_mm(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + bool ret = true; + + /* + * Tell all users of get_user/copy_from_user etc... that the content + * is no longer stable. No barriers really needed because unmapping + * should imply barriers already and the reader would hit a page fault + * if it stumbled over a reaped memory. + */ + set_bit(MMF_UNSTABLE, &mm->flags); + + for (vma = mm->mmap ; vma; vma = vma->vm_next) { + if (!can_madv_dontneed_vma(vma)) + continue; + + /* + * Only anonymous pages have a good chance to be dropped + * without additional steps which we cannot afford as we + * are OOM already. + * + * We do not even care about fs backed pages because all + * which are reclaimable have already been reclaimed and + * we do not want to block exit_mmap by keeping mm ref + * count elevated without a good reason. + */ + if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) { + const unsigned long start = vma->vm_start; + const unsigned long end = vma->vm_end; + struct mmu_gather tlb; + + tlb_gather_mmu(&tlb, mm, start, end); + if (mmu_notifier_invalidate_range_start_nonblock(mm, start, end)) { + tlb_finish_mmu(&tlb, start, end); + ret = false; + continue; + } + unmap_page_range(&tlb, vma, start, end, NULL); + mmu_notifier_invalidate_range_end(mm, start, end); + tlb_finish_mmu(&tlb, start, end); + } + } + + return ret; +} + +/* + * Reaps the address space of the give task. + * + * Returns true on success and false if none or part of the address space + * has been reclaimed and the caller should retry later. + */ +static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) +{ + bool ret = true; + + if (!down_read_trylock(&mm->mmap_sem)) { + trace_skip_task_reaping(tsk->pid); + return false; + } + + /* + * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't + * work on the mm anymore. The check for MMF_OOM_SKIP must run + * under mmap_sem for reading because it serializes against the + * down_write();up_write() cycle in exit_mmap(). + */ + if (test_bit(MMF_OOM_SKIP, &mm->flags)) { + trace_skip_task_reaping(tsk->pid); + goto out_unlock; + } + + trace_start_task_reaping(tsk->pid); + + /* failed to reap part of the address space. Try again later */ + ret = __oom_reap_task_mm(mm); + if (!ret) + goto out_finish; + + pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", + task_pid_nr(tsk), tsk->comm, + K(get_mm_counter(mm, MM_ANONPAGES)), + K(get_mm_counter(mm, MM_FILEPAGES)), + K(get_mm_counter(mm, MM_SHMEMPAGES))); +out_finish: + trace_finish_task_reaping(tsk->pid); +out_unlock: + up_read(&mm->mmap_sem); + + return ret; +} + +#define MAX_OOM_REAP_RETRIES 10 +static void oom_reap_task(struct task_struct *tsk) +{ + int attempts = 0; + struct mm_struct *mm = tsk->signal->oom_mm; + + /* Retry the down_read_trylock(mmap_sem) a few times */ + while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm)) + schedule_timeout_idle(HZ/10); + + if (attempts <= MAX_OOM_REAP_RETRIES || + test_bit(MMF_OOM_SKIP, &mm->flags)) + goto done; + + pr_info("oom_reaper: unable to reap pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); + debug_show_all_locks(); + +done: + tsk->oom_reaper_list = NULL; + + /* + * Hide this mm from OOM killer because it has been either reaped or + * somebody can't call up_write(mmap_sem). + */ + set_bit(MMF_OOM_SKIP, &mm->flags); + + /* Drop a reference taken by wake_oom_reaper */ + put_task_struct(tsk); +} + +static int oom_reaper(void *unused) +{ + while (true) { + struct task_struct *tsk = NULL; + + wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL); + spin_lock(&oom_reaper_lock); + if (oom_reaper_list != NULL) { + tsk = oom_reaper_list; + oom_reaper_list = tsk->oom_reaper_list; + } + spin_unlock(&oom_reaper_lock); + + if (tsk) + oom_reap_task(tsk); + } + + return 0; +} + +static void wake_oom_reaper(struct task_struct *tsk) +{ + /* mm is already queued? */ + if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) + return; + + get_task_struct(tsk); + + spin_lock(&oom_reaper_lock); + tsk->oom_reaper_list = oom_reaper_list; + oom_reaper_list = tsk; + spin_unlock(&oom_reaper_lock); + trace_wake_reaper(tsk->pid); + wake_up(&oom_reaper_wait); +} + +static int __init oom_init(void) +{ + oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper"); + return 0; +} +subsys_initcall(oom_init) +#else +static inline void wake_oom_reaper(struct task_struct *tsk) +{ +} +#endif /* CONFIG_MMU */ + +/** + * mark_oom_victim - mark the given task as OOM victim + * @tsk: task to mark + * + * Has to be called with oom_lock held and never after + * oom has been disabled already. + * + * tsk->mm has to be non NULL and caller has to guarantee it is stable (either + * under task_lock or operate on the current). + */ +static void mark_oom_victim(struct task_struct *tsk) +{ + struct mm_struct *mm = tsk->mm; + + WARN_ON(oom_killer_disabled); + /* OOM killer might race with memcg OOM */ + if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) + return; + + /* oom_mm is bound to the signal struct life time. */ + if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) { + mmgrab(tsk->signal->oom_mm); + set_bit(MMF_OOM_VICTIM, &mm->flags); + } + + /* + * Make sure that the task is woken up from uninterruptible sleep + * if it is frozen because OOM killer wouldn't be able to free + * any memory and livelock. freezing_slow_path will tell the freezer + * that TIF_MEMDIE tasks should be ignored. + */ + __thaw_task(tsk); + atomic_inc(&oom_victims); + trace_mark_victim(tsk->pid); +} + +/** + * exit_oom_victim - note the exit of an OOM victim + */ +void exit_oom_victim(void) +{ + clear_thread_flag(TIF_MEMDIE); + + if (!atomic_dec_return(&oom_victims)) + wake_up_all(&oom_victims_wait); +} + +/** + * oom_killer_enable - enable OOM killer + */ +void oom_killer_enable(void) +{ + oom_killer_disabled = false; + pr_info("OOM killer enabled.\n"); +} + +/** + * oom_killer_disable - disable OOM killer + * @timeout: maximum timeout to wait for oom victims in jiffies + * + * Forces all page allocations to fail rather than trigger OOM killer. + * Will block and wait until all OOM victims are killed or the given + * timeout expires. + * + * The function cannot be called when there are runnable user tasks because + * the userspace would see unexpected allocation failures as a result. Any + * new usage of this function should be consulted with MM people. + * + * Returns true if successful and false if the OOM killer cannot be + * disabled. + */ +bool oom_killer_disable(signed long timeout) +{ + signed long ret; + + /* + * Make sure to not race with an ongoing OOM killer. Check that the + * current is not killed (possibly due to sharing the victim's memory). + */ + if (mutex_lock_killable(&oom_lock)) + return false; + oom_killer_disabled = true; + mutex_unlock(&oom_lock); + + ret = wait_event_interruptible_timeout(oom_victims_wait, + !atomic_read(&oom_victims), timeout); + if (ret <= 0) { + oom_killer_enable(); + return false; + } + pr_info("OOM killer disabled.\n"); + + return true; +} + +static inline bool __task_will_free_mem(struct task_struct *task) +{ + struct signal_struct *sig = task->signal; + + /* + * A coredumping process may sleep for an extended period in exit_mm(), + * so the oom killer cannot assume that the process will promptly exit + * and release memory. + */ + if (sig->flags & SIGNAL_GROUP_COREDUMP) + return false; + + if (sig->flags & SIGNAL_GROUP_EXIT) + return true; + + if (thread_group_empty(task) && (task->flags & PF_EXITING)) + return true; + + return false; +} + +/* + * Checks whether the given task is dying or exiting and likely to + * release its address space. This means that all threads and processes + * sharing the same mm have to be killed or exiting. + * Caller has to make sure that task->mm is stable (hold task_lock or + * it operates on the current). + */ +static bool task_will_free_mem(struct task_struct *task) +{ + struct mm_struct *mm = task->mm; + struct task_struct *p; + bool ret = true; + + /* + * Skip tasks without mm because it might have passed its exit_mm and + * exit_oom_victim. oom_reaper could have rescued that but do not rely + * on that for now. We can consider find_lock_task_mm in future. + */ + if (!mm) + return false; + + if (!__task_will_free_mem(task)) + return false; + + /* + * This task has already been drained by the oom reaper so there are + * only small chances it will free some more + */ + if (test_bit(MMF_OOM_SKIP, &mm->flags)) + return false; + + if (atomic_read(&mm->mm_users) <= 1) + return true; + + /* + * Make sure that all tasks which share the mm with the given tasks + * are dying as well to make sure that a) nobody pins its mm and + * b) the task is also reapable by the oom reaper. + */ + rcu_read_lock(); + for_each_process(p) { + if (!process_shares_mm(p, mm)) + continue; + if (same_thread_group(task, p)) + continue; + ret = __task_will_free_mem(p); + if (!ret) + break; + } + rcu_read_unlock(); + + return ret; +} + +static void __oom_kill_process(struct task_struct *victim) +{ + struct task_struct *p; + struct mm_struct *mm; + bool can_oom_reap = true; + + p = find_lock_task_mm(victim); + if (!p) { + put_task_struct(victim); + return; + } else if (victim != p) { + get_task_struct(p); + put_task_struct(victim); + victim = p; + } + + /* Get a reference to safely compare mm after task_unlock(victim) */ + mm = victim->mm; + mmgrab(mm); + + /* Raise event before sending signal: task reaper must see this */ + count_vm_event(OOM_KILL); + memcg_memory_event_mm(mm, MEMCG_OOM_KILL); + + /* + * We should send SIGKILL before granting access to memory reserves + * in order to prevent the OOM victim from depleting the memory + * reserves from the user space under its control. + */ + do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, PIDTYPE_TGID); + mark_oom_victim(victim); + pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", + task_pid_nr(victim), victim->comm, K(victim->mm->total_vm), + K(get_mm_counter(victim->mm, MM_ANONPAGES)), + K(get_mm_counter(victim->mm, MM_FILEPAGES)), + K(get_mm_counter(victim->mm, MM_SHMEMPAGES))); + task_unlock(victim); + + /* + * Kill all user processes sharing victim->mm in other thread groups, if + * any. They don't get access to memory reserves, though, to avoid + * depletion of all memory. This prevents mm->mmap_sem livelock when an + * oom killed thread cannot exit because it requires the semaphore and + * its contended by another thread trying to allocate memory itself. + * That thread will now get access to memory reserves since it has a + * pending fatal signal. + */ + rcu_read_lock(); + for_each_process(p) { + if (!process_shares_mm(p, mm)) + continue; + if (same_thread_group(p, victim)) + continue; + if (is_global_init(p)) { + can_oom_reap = false; + set_bit(MMF_OOM_SKIP, &mm->flags); + pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", + task_pid_nr(victim), victim->comm, + task_pid_nr(p), p->comm); + continue; + } + /* + * No use_mm() user needs to read from the userspace so we are + * ok to reap it. + */ + if (unlikely(p->flags & PF_KTHREAD)) + continue; + do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, PIDTYPE_TGID); + } + rcu_read_unlock(); + + if (can_oom_reap) + wake_oom_reaper(victim); + + mmdrop(mm); + put_task_struct(victim); +} +#undef K + +/* + * Kill provided task unless it's secured by setting + * oom_score_adj to OOM_SCORE_ADJ_MIN. + */ +static int oom_kill_memcg_member(struct task_struct *task, void *unused) +{ + if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN && + !is_global_init(task)) { + get_task_struct(task); + __oom_kill_process(task); + } + return 0; +} + +static void oom_kill_process(struct oom_control *oc, const char *message) +{ + struct task_struct *p = oc->chosen; + unsigned int points = oc->chosen_points; + struct task_struct *victim = p; + struct task_struct *child; + struct task_struct *t; + struct mem_cgroup *oom_group; + unsigned int victim_points = 0; + static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + + /* + * If the task is already exiting, don't alarm the sysadmin or kill + * its children or threads, just give it access to memory reserves + * so it can die quickly + */ + task_lock(p); + if (task_will_free_mem(p)) { + mark_oom_victim(p); + wake_oom_reaper(p); + task_unlock(p); + put_task_struct(p); + return; + } + task_unlock(p); + + if (__ratelimit(&oom_rs)) + dump_header(oc, p); + + pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n", + message, task_pid_nr(p), p->comm, points); + + /* + * If any of p's children has a different mm and is eligible for kill, + * the one with the highest oom_badness() score is sacrificed for its + * parent. This attempts to lose the minimal amount of work done while + * still freeing memory. + */ + read_lock(&tasklist_lock); + + /* + * The task 'p' might have already exited before reaching here. The + * put_task_struct() will free task_struct 'p' while the loop still try + * to access the field of 'p', so, get an extra reference. + */ + get_task_struct(p); + for_each_thread(p, t) { + list_for_each_entry(child, &t->children, sibling) { + unsigned int child_points; + + if (process_shares_mm(child, p->mm)) + continue; + /* + * oom_badness() returns 0 if the thread is unkillable + */ + child_points = oom_badness(child, + oc->memcg, oc->nodemask, oc->totalpages); + if (child_points > victim_points) { + put_task_struct(victim); + victim = child; + victim_points = child_points; + get_task_struct(victim); + } + } + } + put_task_struct(p); + read_unlock(&tasklist_lock); + + /* + * Do we need to kill the entire memory cgroup? + * Or even one of the ancestor memory cgroups? + * Check this out before killing the victim task. + */ + oom_group = mem_cgroup_get_oom_group(victim, oc->memcg); + + __oom_kill_process(victim); + + /* + * If necessary, kill all tasks in the selected memory cgroup. + */ + if (oom_group) { + mem_cgroup_print_oom_group(oom_group); + mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, NULL); + mem_cgroup_put(oom_group); + } +} + +/* + * Determines whether the kernel must panic because of the panic_on_oom sysctl. + */ +static void check_panic_on_oom(struct oom_control *oc, + enum oom_constraint constraint) +{ + if (likely(!sysctl_panic_on_oom)) + return; + if (sysctl_panic_on_oom != 2) { + /* + * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel + * does not panic for cpuset, mempolicy, or memcg allocation + * failures. + */ + if (constraint != CONSTRAINT_NONE) + return; + } + /* Do not panic for oom kills triggered by sysrq */ + if (is_sysrq_oom(oc)) + return; + dump_header(oc, NULL); + panic("Out of memory: %s panic_on_oom is enabled\n", + sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); +} + +static BLOCKING_NOTIFIER_HEAD(oom_notify_list); + +int register_oom_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&oom_notify_list, nb); +} +EXPORT_SYMBOL_GPL(register_oom_notifier); + +int unregister_oom_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_unregister(&oom_notify_list, nb); +} +EXPORT_SYMBOL_GPL(unregister_oom_notifier); + +/** + * out_of_memory - kill the "best" process when we run out of memory + * @oc: pointer to struct oom_control + * + * If we run out of memory, we have the choice between either + * killing a random task (bad), letting the system crash (worse) + * OR try to be smart about which process to kill. Note that we + * don't have to be perfect here, we just have to be good. + */ +bool out_of_memory(struct oom_control *oc) +{ + unsigned long freed = 0; + enum oom_constraint constraint = CONSTRAINT_NONE; + + if (oom_killer_disabled) + return false; + + if (!is_memcg_oom(oc)) { + blocking_notifier_call_chain(&oom_notify_list, 0, &freed); + if (freed > 0) + /* Got some memory back in the last second. */ + return true; + } + + /* + * If current has a pending SIGKILL or is exiting, then automatically + * select it. The goal is to allow it to allocate so that it may + * quickly exit and free its memory. + */ + if (task_will_free_mem(current)) { + mark_oom_victim(current); + wake_oom_reaper(current); + return true; + } + + /* + * The OOM killer does not compensate for IO-less reclaim. + * pagefault_out_of_memory lost its gfp context so we have to + * make sure exclude 0 mask - all other users should have at least + * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to + * invoke the OOM killer even if it is a GFP_NOFS allocation. + */ + if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc)) + return true; + + /* + * Check if there were limitations on the allocation (only relevant for + * NUMA and memcg) that may require different handling. + */ + constraint = constrained_alloc(oc); + if (constraint != CONSTRAINT_MEMORY_POLICY) + oc->nodemask = NULL; + check_panic_on_oom(oc, constraint); + + if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task && + current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) && + current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { + get_task_struct(current); + oc->chosen = current; + oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)"); + return true; + } + + select_bad_process(oc); + /* Found nothing?!?! */ + if (!oc->chosen) { + dump_header(oc, NULL); + pr_warn("Out of memory and no killable processes...\n"); + /* + * If we got here due to an actual allocation at the + * system level, we cannot survive this and will enter + * an endless loop in the allocator. Bail out now. + */ + if (!is_sysrq_oom(oc) && !is_memcg_oom(oc)) + panic("System is deadlocked on memory\n"); + } + if (oc->chosen && oc->chosen != (void *)-1UL) + oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" : + "Memory cgroup out of memory"); + return !!oc->chosen; +} + +/* + * The pagefault handler calls here because some allocation has failed. We have + * to take care of the memcg OOM here because this is the only safe context without + * any locks held but let the oom killer triggered from the allocation context care + * about the global OOM. + */ +void pagefault_out_of_memory(void) +{ + static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + + if (mem_cgroup_oom_synchronize(true)) + return; + + if (fatal_signal_pending(current)) + return; + + if (__ratelimit(&pfoom_rs)) + pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n"); +} |